Can I swap a 9 speed Sora rear for a 105 10 speed?

[Dave_C]

Following a discussion on FB Audax Tech page.

My ~5 yr old 105 rear derailleur has lots of play. I have a new (unused in my spares draw) 9 speed? sora rear derailleur. Can I do a straight swap and it work?

Cheers.

Sent from my A0001 using Tapatalk

[LittleWheelsandBig]

Yes

[Oxford_Guy]

Yes, because Shimano road rear derailleurs all have the same 1.7 shift ratio 6-10 speed (not the case for MTB 10-speed or road 11-speed, though).

See: http://blog.artscyclery.com/science-behind-the-magic/science-behind-the-magic-drivetrain-compatibility/

Not 100% sure if you'd loose the ability to shift into the 10th sprocket or not, though.

[Brucey]

the first gear sprocket in a 10s cluster is about 1mm closer to the spokes so a 9s mech has to move fractionally further and be fractionally closer to the spokes than intended when used in a 10s setup. But it normally works out OK, and the shift ratios match etc.  It isn't a bad idea to fit 10s pulleys when the originals wear out.

cheers

[yoav]

Should be fine. I have a 9 speed Shimano MTB rear mech with a 10 speed Shimano road cassette and 10 speed road shifter - they all work together without problems.

[Dave_C]

Great!! Many thanks for the positive replies. I'll change over the mech tomorrow when we arrive in Belgium.

Sent from my A0001 using Tapatalk

[citoyen]

Yes, because Shimano road rear derailleurs all have the same 1.7 shift ratio 6-10 speed (not the case for MTB 10-speed or road 11-speed, though).

Except Tiagra 4700 10-speed, which is 1.4, IIRC (same as Shimano road 11-speed).

[ElyDave]

I have an 8-speed Tiagra which was successfully upgraded to 10-speed when the shifter failed.

[Brucey]

Yes, because Shimano road rear derailleurs all have the same 1.7 shift ratio 6-10 speed (not the case for MTB 10-speed or road 11-speed, though).

Except Tiagra 4700 10-speed, which is 1.4, IIRC (same as Shimano road 11-speed).

The other exception is Dura-Ace 7400, 6s, 7s, 8s RDs; these have a higher shift ratio than other shimano RDs.

cheers

[mcshroom]

Yes. I had a Sora 3500 rear on my Raleigh with Tiagra 4600 components otherwise and it worked fine.